Like its hard-wired counterpart, this GENTEX Smoke Alarm with visual signal is designed to alarm a room or home with a piercing loud alarm and very bright strobe. It is sure to capture your attention asleep or while awake. This portable smoke detector is AC powered, so you do not need an electrician to install it. In the event of a power failure the battery backup operates the audible alarm only. This photoelectric single station smoke detector is designed to give reliable early warning of the presence of smoke where both audible and visual alarms are required.